1. Field of the Invention
The present invention relates to a rotating electric machine having a rotational position sensor, and a method and device for positioning the rotational position sensor.
2. Description of the Related Art
A conventional device has been disclosed in JP-A-2002-186239. This conventional device is a brushless motor in which a detection rotor and a rotation axis are provided separately, and the detection rotor is fixed to the rotation axis by an instantaneous adhesive. Also, a method for assembling the brushless motor is disclosed, including fitting the detection rotor with a play to be relatively rotatable around the rotation axis, stopping a driving rotor at a predetermined position by continually supplying a direct current to a partial phase of a driving coil, tentatively deciding the position of the detection rotor by visual inspection so that the relative position between the detection rotor and the detection stator may fall within a tolerance range, generating an electromagnet action by continually supplying a direct current to a partial phase of an output coil, modifying the relative position between the detection rotor and the detection stator to be in a predetermined position by the movement of the detection rotor based on this electromagnet action, fixing the detection rotor to the rotation axis, and ceasing the supply of direct current to the driving coil and the output coil after completion of fixing.
The conventional brushless motor and the method for assembling the brushless motor are not suitable for the rotating electric machine for vehicle that is subjected to severe vibration and heat, because the detection rotor is fixed to the rotation axis by instantaneous adhesive. The driving rotor is stopped at a predetermined position by continually supplying a direct current to a partial phase of the driving coil, but actually, owing to a rotational friction force of bearings rotatably supporting the rotation axis as well as a rotational friction force produced in a structure in which a brush is rubbed against a slit ring fixed to the rotation axis such as an alternator for vehicle, the driving rotor can not be stopped at the predetermined intrinsic position accurately and stably simply by continually supplying a direct current to a partial phase of the driving coil, resulting in a problem that the rotational position sensor has a poor positioning precision, and the rotating electric machine has a degraded or insufficient performance. Moreover, there is another problem that the step of positioning is lengthened, and it in unsuitable for automation.